KR101181148B1 - Lithium ion conducting sulfide based crystallized glass and method for production thereof - Google Patents

Abstract

The present invention contains lithium (Li), phosphorus (P) and sulfur (S) elements as constituents, and 2θ = 17.8 ± 0.3deg, 18.2 ± 0.3deg, in X-ray diffraction (CuKα: λ = 1.5418 Hz). A lithium ion conductive sulfide-based crystallized glass having diffraction peaks at 19.8 ± 0.3deg, 21.8 ± 0.3deg, 23.8 ± 0.3deg, 25.9 ± 0.3deg, 29.5 ± 0.3deg and 30.0 ± 0.3deg.

Description

Lithium ion conductive sulfide-based crystallized glass and a method of manufacturing the same {LITHIUM ION CONDUCTING SULFIDE BASED CRYSTALLIZED GLASS AND METHOD FOR PRODUCTION THEREOF}

The present invention relates to a lithium ion conductive sulfide-based crystallized glass, a method for producing the same, and a solid electrolyte and an all-solid-state battery using the same.

In the past, electrolytes exhibiting high lithium ion conductivity at room temperature were mostly limited to liquids. For example, there is an organic electrolyte solution as a material exhibiting high lithium ion conductivity at room temperature.

In addition, a lithium ion conductive ceramic based on Li ₃ N, which exhibits high conductivity of 10 ⁻³ Scm ⁻¹ or higher at room temperature, is known.

However, the conventional organic electrolyte solution is flammable because it contains an organic solvent. Therefore, when the ion conductive material containing the organic solvent is actually used as the electrolyte of the battery, there is a risk of liquid leakage or a risk of ignition.

In addition, since such an electrolyte solution is a liquid, lithium ion yield is not 1 because not only lithium ions are conducted but also counter ions are conducted.

Since a lithium ion conductive ceramic based on conventional Li ₃ N has a low decomposition voltage, it is difficult to construct an all-solid-state battery that operates at 3 V or more.

As for such a problem, Li ₂ S 50 to 92.5 mol% and P ₂ S ₅ 7.5 as to the composition of 50 mol% has a crystallization rate of 30 to 99% glass phase composed mainly of Li ₂ S and P ₂ S ₅ and, Sulfide-based crystallized glass in which a crystal phase containing at least one compound selected from the group consisting of Li ₇ PS ₆ , Li ₄ P ₂ S ₆ and Li ₃ PS ₄ is present is disclosed (for example, Japanese Patent Application Laid-Open No. 2002). -109955).

This sulfide-based crystalline glass shows high lithium ion conductivity even at room temperature.

However, when manufacturing this crystal type glass, the heat processing temperature is 500 degreeC or more, and when manufacturing industrially, a special installation is needed. In addition, the region showing high ionic conductivity is composed of 80 mol% Li ₂ S and 20 mol% P ₂ S ₅ , so that an expensive Li source is used in a large amount.

For this reason, the manufacturing cost of a material became expensive and it was not necessarily satisfactory in economy.

Moreover, in order to improve the efficiency of the lithium secondary battery using sulfide system crystalline glass, the material which has higher lithium ion conductivity is calculated | required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and exhibits extremely high lithium ion conductivity even at room temperature, and enables industrial production by lowering the heat treatment temperature and reducing the amount of Li source used. The purpose is to provide.

DISCLOSURE OF INVENTION

In order to solve this problem, the present inventors have studied in detail the technique described in Japanese Patent Laid-Open No. 2002-109955, and as a result, sulfide-based crystalline glass in a composition having a low heat treatment temperature and a relatively low amount of Li source is used. Discovered a novel crystal structure and found that lithium ion conductivity was remarkably excellent when it had this crystal structure, and completed this invention.

That is, according to this invention, the lithium ion conductive sulfide type crystallized glass shown below, its manufacturing method, and the solid electrolyte and all-solid-state battery using the same are provided.

1.Contains lithium (Li), phosphorus (P) and sulfur (S) elements as constituents, and 2θ = 17.8 ± 0.3deg, 18.2 ± 0.3deg, 19.8 in X-ray diffraction (CuKα: λ = 1.5418 Hz) Lithium ion conductive sulfide-based crystallized glass having diffraction peaks at ± 0.3deg, 21.8 ± 0.3deg, 23.8 ± 0.3deg, 25.9 ± 0.3deg, 29.5 ± 0.3deg and 30.0 ± 0.3deg.

2. Li ₂ S: 68 to 74 mol% and P ₂ S ₅ : 26 to 32 mol% A method for producing a lithium ion conductive sulfide-based crystallized glass by calcining at 150 to 360 ° C.

3. The Li ₂ S is, aprotic lithium ion conductivity according to Li ₂ S obtained by reacting lithium hydroxide with hydrogen sulfide in an organic solvent, the 2 by using an organic solvent that was purified by washing at least 100 ℃ temperature Method for producing sulfide-based crystallized glass.

4. The method for producing a lithium ion conductive sulfide-based crystallized glass according to 2 or 3, wherein the total amount of sulfur oxide contained in Li ₂ S is 0.15% by mass or less, and lithium N-methylaminobutyrate (LMAB) is 0.1% by mass or less. .

5. The method for producing a lithium ion conductive sulfide-based crystallized glass according to any one of the above 2 to 4, using single phosphorus (P) and single sulfur (S) in a corresponding molar ratio instead of P ₂ S ₅ .

6. The sulfide system according to any one of the above 2 to 5, wherein the Li ₂ S and P ₂ S ₅ or single phosphorus (P) and single sulfur (S) are made into the sulfide-based glass by mechanical milling. Method for producing crystallized glass.

7. Lithium ion conductive sulfide type crystallized glass manufactured by the manufacturing method in any one of said 2-6.

8. Solid electrolyte for lithium secondary batteries which use the lithium ion conductive sulfide system crystallization glass of 1 or 7 as a raw material.

9. The all-solid-state battery using the solid electrolyte for lithium secondary batteries of said 8.

The sulfide-based crystalline glass of the present invention and the method for producing the same have a low temperature region with a firing temperature of 150 ° C to 360 ° C, and the amount of Li source used can be reduced, so that industrial production is possible and the economy is excellent.

Moreover, since extremely high lithium ion conductivity is shown even at room temperature, the performance of the lithium secondary battery using this sulfide type crystalline glass can be improved.

1 is an X-ray diffraction spectrum chart of sulfide-based glass prepared in Example 1 and Comparative Examples 1 to 3. FIG.

2 is an X-ray diffraction spectrum chart of sulfide-based crystallized glass prepared in Example 1 and Comparative Examples 1 to 4. FIG.

It is a figure which shows the measurement result of the ion conductivity of the sulfide system crystallized glass produced in Example 2. FIG.

Hereinafter, the present invention will be described in detail.

The lithium ion conductive sulfide-based crystallized glass of the present invention contains lithium, phosphorus and sulfur elements as constituents, and 2θ = 17.8 ± 0.3deg, 18.2 ± 0.3deg, in X-ray diffraction (CuKα: λ = 1.5418 Hz). It has diffraction peaks at 19.8 ± 0.3deg, 21.8 ± 0.3deg, 23.8 ± 0.3deg, 25.9 ± 0.3deg, 29.5 ± 0.3deg and 30.0 ± 0.3deg.

Crystal structures having diffraction peaks in the above eight regions have not been observed in the past, indicating that the sulfide-based crystallized glass has a novel crystal structure. The present invention finds that sulfide-based crystallized glass having such a crystal structure has extremely high lithium ion conductivity.

This crystal structure can be expressed by calcining a sulfide-based glass having a starting material of a composition of Li ₂ S: 68 to 74 mol% and P ₂ S ₅ : 26 to 32 mol% at 150 to 360 ° C.

As the starting material Li ₂ S, for example, one obtained by washing Li ₂ S obtained by reacting lithium hydroxide and hydrogen sulfide in an aprotic organic solvent at a temperature of 100 ° C. or higher using an organic solvent can be used.

Specifically, it is preferable to manufacture Li ₂ S by the production method disclosed in Japanese Patent Application Laid-Open No. 195-330312, and it is preferable that the Li ₂ S is purified by the method described in Japanese Patent Application No. 2003-363403. .

In this method for producing Li ₂ S, since high purity lithium sulfide can be obtained by simple means, the raw material cost of the sulfide-based crystallized glass can be reduced. In addition, since the above purification method can remove sulfur oxides, lithium N-methylaminobutyrate (hereinafter referred to as LMAB) and the like which are impurities contained in Li ₂ S by a simple treatment, it is economically advantageous, In the solid electrolyte for lithium secondary batteries using the obtained high purity lithium sulfide, the performance fall due to purity is suppressed, and as a result, an excellent lithium secondary battery (solid battery) can be obtained.

In addition, the total amount of sulfur oxides contained in the Li ₂ S is preferably not more than 0.15 mass%, LMAB is preferably 0.1 mass% or less.

P ₂ S ₅ can be used without particular limitation as long as it is industrially produced and sold.

In addition, instead of P ₂ S ₅ , equivalent molar ratios of single phosphorus (P) and single sulfur (S) can be used. Thereby, the sulfide-type crystallized glass of this invention can be manufactured from a material which is easy to obtain and inexpensive. Single phosphorus (P) and single sulfur (S) are industrially produced and sold, and can be used without particular limitation.

The starting material of the sulfide-based crystallized glass of the present invention is composed of Li ₂ S: 68 to 74 mol% and P ₂ S ₅ : 32 to 26 mol%. If it is out of the range of this compounding ratio, the crystal structure peculiar to this invention will not be expressed, ionic conductivity will become small and it will not exhibit sufficient performance as a solid electrolyte. In particular, the amount of the Li ₂ S to 68 to 73 mol%, it is preferable that the compounding amount of the P ₂ S ₅ in 32 to 27 mol%.

Further, in a range capable of expressing a crystal structure having the crystallized glass of the present invention, the P ₂ S ₅ and Li the group consisting of Al ₂ S _3, B ₂ S _3, GeS ₂ and SiS ₂ as the starting material in addition to ₂ S One or more sulfides selected from may be included. When such sulfide is added, more stable glass can be produced when forming sulfide type glass.

Similarly, in addition to Li ₂ S and P ₂ S ₅ , at least one lithium ortho oxate selected from the group consisting of Li ₃ PO ₄ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , Li ₃ BO _3, and Li ₃ AlO ₃ It may include. Inclusion of such lithium ortho lithium oxate can stabilize the glass in the crystallized glass.

Further, in addition to Li ₂ S and P ₂ S _5, it may be included to include the above-described sulfide at least one or more, also, at least one or more of ortho-oxo lithium described above.

As a method for producing sulfide-based glass using the mixture of the above starting materials, for example, mechanical grinding treatment (hereinafter sometimes referred to as MM treatment) or a melt-quenching method is used.

It is preferable to form a sulfide-based glass using the MM treatment because the glass generation region can be enlarged. In addition, since the heat treatment performed by the melt quenching method is unnecessary and can be performed at room temperature, the manufacturing process can be simplified.

When forming a sulfide type glass by melt quenching or MM treatment, it is preferable to use an atmosphere of inert gas such as nitrogen. This is because steam or oxygen easily reacts with the starting materials.

In the MM treatment, it is preferable to use a ball mill. This is because a large mechanical energy can be obtained.

As the ball mill, it is preferable to use a planetary ball mill. In the planetary ball mill, since the plate rotates while the port rotates, very high impact energy can be generated efficiently.

The conditions for the MM treatment can be appropriately adjusted by an apparatus to be used. The faster the rotational speed, the faster the formation rate of the sulfide-based glass, and the longer the rotational time, the higher the raw material conversion rate into the sulfide-based glass. For example, in the case of using a general planetary ball mill, the rotational speed may be set to several tens to several hundred revolutions / minute, and may be treated for 0.5 to 1100 hours.

The obtained sulfide-based glass is calcined to crystallize to obtain the lithium ion conductive sulfide-based crystallized glass of the present invention. The baking temperature at this time is 150 to 360 degreeC. If it is less than 150 degreeC, since it is the temperature below the glass transition point of sulfide type glass, crystallization does not advance. On the other hand, when it exceeds 360 degreeC, the crystal glass which has the crystal structure peculiar to this invention mentioned above is not produced | generated, and will change to the crystal structure of Unexamined-Japanese-Patent No. 2002-109955. The firing temperature is particularly preferably in the range of 200 ° C to 350 ° C. The firing time is not particularly limited as long as it is a condition under which crystals are formed, and may be instant or long time. Moreover, there is no special limitation also regarding the temperature rising pattern to baking temperature.

The sulfide-based crystallized glass of the present invention has a decomposition voltage of at least 5 V or more, is a non-flammable inorganic solid, and maintains a property of lithium ion yield of 1, while being extremely high at 10 ⁻³ Scm ⁻¹ at room temperature. It exhibits lithium ion conductivity. Therefore, it is extremely suitable as a material for solid electrolytes of lithium batteries.

In addition, the all-solid-state battery using the solid electrolyte of the present invention having the above characteristics has high energy density, and is excellent in safety and charge / discharge cycle characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Manufacturing example

(1) Preparation of Lithium Sulfide (Li ₂ S)

Lithium sulfide was manufactured according to the method of the 1st aspect (two process method) of Unexamined-Japanese-Patent No. 195-330312. Specifically, 3326.4 g (33.6 mol) of N-methyl-2-pyrrolidone (NMP) and 287.4 g (12 mol) of lithium hydroxide were filled in a 10 liter autoclave equipped with a stirring blade, and the temperature was raised to 130 ° C. at 300 rpm. did. After the temperature was raised, hydrogen sulfide was blown into the solution at a feed rate of 3 liters / minute for 2 hours. Subsequently, the reaction solution was heated up under a nitrogen stream (200 cc / min), and a part of the hydrogen sulfide reacted was dehydrogenated. As the temperature was raised, the by-product water began to evaporate due to the reaction of the hydrogen sulfide and lithium hydroxide, but the water was condensed by a condenser and drawn out of the system. While distilling water out of the system and raising the temperature of the reaction solution, the temperature was stopped when the temperature reached 180 ° C and maintained at a constant temperature. After the desulfurization reaction was completed (about 80 minutes), the reaction was terminated to obtain lithium sulfide.

(2) purification of lithium sulfide

After decantation of NMP in the 500 mL slurry reaction solution (NMP-lithium sulfide slurry) obtained in the above (1), 100 mL of dehydrated NMP was added and stirred at 105 ° C for about 1 hour. NMP was decanted as it was at this temperature. Furthermore, 100 mL of NMP was added, it stirred at 105 degreeC for about 1 hour, NMP was decanted as it was, and the same operation was repeated 4 times in total. After completion of the decantation, the lithium sulfide was dried at atmospheric pressure for 3 hours at 230 ° C. (temperature above the boiling point of NMP) under a nitrogen stream. The impurity content in the obtained lithium sulfide was measured.

In addition, the contents of the respective sulfur oxides of lithium sulfite (Li ₂ SO ₃ ), lithium sulfate (Li ₂ SO ₄ ) and lithium thiosulfate (Li ₂ S ₂ O ₃ ), and lithium N-methylaminobutyrate (LMAB) Quantification was carried out by ion chromatography. As a result, the total content of sulfur oxides was 0.13 mass%, and LMAB was 0.07 mass%.

Thus purified Li ₂ S was used in the following Examples and Comparative Examples.

Example  One

Li ₂ S and P ₂ S ₅ (manufactured by Aldrich) prepared in Preparation Example were used as starting materials. About 1 g of the mixture prepared at a molar ratio of 70 to 30 and 10 alumina balls having a particle diameter of 10 mmΦ were placed in a 45 mL alumina container, and a planetary ball mill (manufactured by Frisch: Type No. P-7) was prepared. It was used to obtain a sulfide-based glass as a white-yellow powder by mechanical grinding treatment for 20 hours at a rotational speed of 370 rpm at room temperature (25 ° C.) in nitrogen.

Powder X-ray diffraction measurement was performed on the obtained powder (CuKα: λ = 1.5418 Hz). This X-ray diffraction spectrum is shown in FIG. 1, the spectrum of Comparative Examples 1-3 mentioned later is also shown.

Since this chart showed the broad form peculiar to an amorphous body, it was confirmed that this powder was vitrified (amorphized).

The powder (sulfide-based glass) was calcined in nitrogen in a temperature range from room temperature (25 ° C.) to 260 ° C. to produce sulfide-based crystallized glass. In addition, differential thermal analysis was performed simultaneously with the firing treatment.

The temperature rising rate and temperature decreasing rate at this time were made into 10 degreeC / min, and it heated up to 260 degreeC, and cooled to room temperature.

As a result of the differential thermal analysis, an exothermic peak accompanied by crystallization of the amorphous body was observed at 230 to 240 ° C. Thereby, it turned out that an amorphous body turns into crystalline glass at 230-240 degreeC.

Powder X-ray diffraction measurement was performed on the sulfide-based crystallized glass prepared above (CuKα: λ = 1.5418 Hz). 2 shows an X-ray diffraction spectrum chart of the sulfide-based crystallized glass. 2, the spectrum of Comparative Examples 1-4 mentioned later is also shown.

From Fig. 2, it was confirmed that the obtained crystallized glass had diffraction peaks at 2θ = 17.8 deg, 18.2 deg, 19.8 deg, 21.8 deg, 23.8 deg, 25.9 deg, 29.5 deg, and 30.0 deg, and Li ₇ PS ₆ known in the art. It was confirmed that the crystal phase was different from that of Li ₄ P ₂ S ₆ and Li ₃ PS ₄ .

Example 2

The sulfide-based glass (powder before firing) produced in Example 1 was processed into a pellet-shaped product (about 10 mm in diameter and about 1 mm in thickness).

About this molded object, ion conductivity was measured, carrying out baking process. The measurement was performed by the alternating current two-terminal method for applying the carbon paste as an electrode to the molded body.

Firing (measurement) was performed by starting at room temperature (25 degreeC), heating up to 25 degreeC vicinity, and then heating to room temperature. At this time, about 3 hours were required for the temperature increase and the temperature.

Fig. 3 is a diagram showing the results of measurement of the ion conductivity of the sulfide-based crystallized glass in an Arrhenius plot.

The ion conductivity of the sulfide-based crystallized glass obtained by this treatment at room temperature (25 ° C.) was 2.1 × 10 ⁻³ Scm ⁻¹ . This value was the largest value in the past in the electrolyte of the present element type (Li, P, S).

As a result of performing X-ray diffraction measurement on the sample after the measurement, it was confirmed that the same diffraction peak pattern as in Example 1 was obtained.

The baking temperature of Example 2 and the comparative example shown below, and the X-ray-diffraction peak, crystal | crystallization, and ion conductivity of the sulfide system crystallized glass produced by each example are shown in Table 1.

Example 3

Crystallized glass was produced in the same manner as in Example 1 except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 68:32.

In the obtained crystallized glass, X-ray diffraction peaks similar to those of Example 1 were observed. In addition, the ion conductivity was measured in the same manner as in Example 2, and the result was 1.0 × 10 ⁻³ S / cm.

Example 4

Crystallized glass was produced in the same manner as in Example 1 except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 73:27.

In the obtained crystallized glass, X-ray diffraction peaks similar to those of Example 1 were observed. Moreover, it was 1.3x10 <^-3> S / cm when the ion conductivity was measured by the method similar to Example 2.

Comparative Example 1

A sulfide-based crystallized glass was produced in the same manner as in Example 1 except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 67:33. In addition, the ion conductivity was measured in the same manner as in Example 2.

Comparative Example 2

A sulfide-based crystallized glass was produced in the same manner as in Example 1 except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 75:25. In addition, the ion conductivity was measured in the same manner as in Example 2.

Comparative Example 3

A sulfide-based crystallized glass was produced in the same manner as in Example 1 except that the molar ratio of Li ₂ S and P ₂ S ₅ was changed to 80:20. In addition, the ion conductivity was measured in the same manner as in Example 2.

Comparative Example 4

In the firing process, sulfide-based crystallized glass was produced in the same manner as in Examples 1 and 2 except that the maximum temperature was changed from 250 ° C. to 550 ° C., and the ion conductivity was measured.

As shown in FIG. 2, it was confirmed that the sulfide-based crystallized glass produced in Comparative Examples 1 to 4 did not show a diffraction peak peculiar to that of the crystallized glass of the present invention.

Moreover, it was confirmed from the measurement result of the ion conductivity of the Example and comparative example which are shown in Table 1 that the sulfide type crystallized glass of this invention shows the extremely high ion conductivity compared with the conventional thing.

The lithium ion conductive sulfide-based crystallized glass of the present invention has a decomposition voltage of at least 5 V or more, is a non-flammable inorganic solid and maintains a property of lithium ion yield of 1, and has not been described as 10 ⁻³ Scm ⁻¹ at room temperature. It exhibits extremely high lithium ion conductivity. Therefore, it is extremely suitable as a material for solid electrolytes of lithium batteries.

Moreover, since the manufacturing method of this invention is a low temperature area | region with a baking temperature of 150 degreeC-360 degreeC, and the usage-amount of Li source can be reduced, industrial production is possible and it is excellent also in economic efficiency.

In addition, the all-solid-state battery using the solid electrolyte of the present invention having the above characteristics has high energy density, and is excellent in safety and charge / discharge cycle characteristics.

Claims (11)

Containing lithium (Li), phosphorus (P) and sulfur (S) elements as constituents, 2θ = 17.8 ± 0.3deg, 18.2 ± 0.3deg, 19.8 ± 0.3 in X-ray diffraction (CuKα: λ = 1.5418 Hz) Lithium ion conductive sulfide-based crystallized glass having diffraction peaks at deg, 21.8 ± 0.3deg, 23.8 ± 0.3deg, 25.9 ± 0.3deg, 29.5 ± 0.3deg and 30.0 ± 0.3deg. A method of producing a lithium ion conductive sulfide-based crystallized glass, wherein the starting material is calcined at 150 to 360 ° C. for a sulfide-based glass having a composition of Li ₂ S: 68 to 74 mol% and P ₂ S ₅ : 26 to 32 mol%. The method of claim 2, The Li ₂ S is, aprotic for producing a lithium ion conductive sulfide-based crystallized glass of Li ₂ S obtained by reacting lithium hydroxide with hydrogen sulfide in an organic solvent, it was purified by using an organic solvent, washing with more than 100 ℃ temperature Way. The method of claim 2, The method of the sulfuric acid and the total amount of cargo than 0.15% by weight, N- methyl amino acid lithium (LMAB) is 0.1 mass% or less of lithium ion conductive sulfide-based crystallized glass is included in the Li ₂ S. The method of claim 2, A method for producing a lithium ion conductive sulfide-based crystallized glass using single phosphorus (P) and single sulfur (S) in equivalent molar ratios instead of the P ₂ S ₅ . The method according to claim 2 or 5, A method for producing sulfide-based crystallized glass, wherein the Li ₂ S and P ₂ S ₅ or single phosphorus (P) and single sulfur (S) are the sulfide-based glass by mechanical grinding. A lithium ion conductive sulfide-based crystallized glass produced by the manufacturing method according to claim 2. A solid electrolyte for a lithium secondary battery using the lithium ion conductive sulfide-based crystallized glass according to claim 1 as a raw material. A solid electrolyte for a lithium secondary battery using the lithium ion conductive sulfide-based crystallized glass according to claim 7 as a raw material. The all-solid-state battery using the solid electrolyte for lithium secondary batteries of Claim 8. The all-solid-state battery using the solid electrolyte for lithium secondary batteries of Claim 9.

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